The trucking industry is one of the primary means of transporting goods and equipment in the United States. In 1994, the trucking industry hauled 5.5 billion tons of freight accounting for 55 percent of the total domestic freight volume. To handle this volume of freight, the trucking industry estimates that it will require 300,000 to 500,000 new truck drivers each year. To attract this workforce, and retain the present workforce, the trucking industry is constantly seeking new ways to improve the working conditions and living quality of heavy trucks for its drivers.
Rough roads, railroad crossing, and the like, cause vibrations that are felt by the occupants of the truck's cab. Road vibration is one of the greatest causes for driver fatigue experienced. Vibrations can be transmitted directly from the road surface to the occupants through the suspension of the truck. However, these same vibrations are also transmitted indirectly through the trailer linkages coupling the trailer to the truck.
Heavy truck drivers commonly operate in two person teams. Frequently, while one person is driving the truck, the other person will sleep in a sleeping compartment at the rear of the cab. It is therefore desirable, both for the on-duty driver, and the off-duty driver sleeping, to stabilize the movement of the truck cab and minimize the vibrations and oscillations caused by rough surfaces. One primary method of achieving this goal is through minimizing the transmission of the trailer's vibrations and oscillations to the truck cab. Therefore, there is a current and continuing need for structures and mechanisms that will reduce the amount of road vibration felt by occupants of a truck.
In the current state of heavy truck technology, the truck is comprised of a cab attached to the front end of a single rigid frame. The heavy truck attaches and holds a trailer through a fifth wheel coupler mounted at the rear of the truck frame. The fifth wheel couples the truck frame to the kingpin of the trailer.
When travelling across a road, a truck and trailer will frequently drive over minor road imperfections such as concrete seams and potholes. A road imperfection that is symmetrically impacted by the trailer, such as a concrete seam, will cause the trailer to vibrate vertically, or to rock about a transverse axis. A road imperfection that is asymmetrically impacted by the trailer, such as a single pothole, will cause the trailer to have both a transverse and a longitudinal axis of motion. Due to the trailer's mechanical engagement with the truck, these mechanical vibrations and oscillations of the trailer are transmitted to the truck and the passenger cab. This transmission of vibrations and oscillations to the cab disturbs the smooth ride for the driver and passengers.
There have been truck designs that attempt to minimize the transmission of trailer vibrations and oscillations through pivotally mounting the fifth wheel with ball joints. The motion of the pivotally mounted fifth wheel is then dampened with hydraulic cylinders. In contrast, the present invention utilizes a split-frame system to minimize the transmission of trailer vibrations. This split-frame system reduces the transmission of road vibrations by mounting the front and rear axles of the truck on two separate moveably interlocked frames.
Inventors have developed many other devices that reduce the transmission of road vibrations to the trailer and the truck cab to enhance the ride quality for both the drivers and the freight. Halvorsen et al., U.S. Pat. No. 5,330,222, discloses a frame isolation system which enhances the ride quality of a terminal tractor. This patent discloses a single tractor frame assembly that includes an axle saddle provided with leading and trailing anti-torque links which permit the axle to move through a limited displacement to compensate for rough and uneven road surfaces. In contrast to the present invention, this patent does not teach the mounting of the front and rear axles on separate frames to reduce the transmission of trailer vibrations to the passenger cab.
A flexible joint assembly used in tandem wheel and axle suspensions for suspending a vehicle chassis is disclosed in Jable et al., U.S. Pat. No. 5,078,420. This patent discloses the pivotal mounting of equalizer leaf springs to a chassis side rail. The dual wheels of this device are separately mounted and separately flexible.
A frame/subframe assembly for mounting an engine and rear wheels to a race car chassis is disclosed in Huszr, U.S. Pat. No. 3,806,149. This patent discloses that the racecar engine and rear wheels are mounted to a subframe made of two side rails. The subframe is spring-mounted in the front and pivotally mounted at the rear to the main frame. The subframe is pivotally mounted with bolts to the mainframe at a point below and forward of the rear axle. The stated object of this subframe system is to provide a structure that allows for engine and chassis torque. A further object of this suspension is to provide a wheeled subframe for the engine to facilitate the repair and maintenance on the engine. This patent does not teach the use of a split-frame system, as in the present invention, to reduce the transmission of vibrations between a trailer and a heavy truck cab.
The present state of the art for motor vehicle frame systems fails to teach a heavy truck that includes a split-frame system mounting the front and rear axles on separate frames that reduces the transmission of transverse vibrations from the trailer to the truck cab. In addition, the present state of the art fails to disclose a split-frame system that also reduces the transmission of rotational vibrations from the trailer to the truck cab.